A disk in a disk drive is coated with a magnetic material which is magnetized with a write head in order to record information onto the surface of the disk. Various influences may render portions of the disk surface unusable (i.e., defective), for example, if the magnetic coating is not evenly applied to the disk surface or if a particle contaminates the magnetic coating. During a manufacturing media defect scan procedure, the defective areas of the disk are located and mapped out so they are not used during normal operation. The defect scan typically involves writing a high frequency pattern (e.g., a 2T pattern) to the disk, and then reading the high frequency pattern while monitoring a quality metric, such as an amplitude of the read signal, a mean-squared-error of the read signal, a bit error of the read signal, a timing error of the read signal, or the output of defect scan filters having impulse responses matched to defect signatures. If the quality metric falls below a predetermined defect scan threshold, a defect is detected.
A media defect scan is typically a dedicated test process that takes a significant time to complete (e.g., hours for a single disk). If the defect scan is simply removed to reduce the test time of a drive, then many defect areas on the disk may not be found and mapped out. The drive may be unable to recover user data written to the defect areas, resulting in data loss.
Accordingly, there is a need to reduce the test time of a drive while providing improved detection of defect areas on the disk.